The capture of dolphins for entertainment is controversial

Around 200 animals are reportedly being held in small, shallow pens after being captured off the Pacific nation, which is currently in political turmoil.

Australia urged Mexico to block the importation of the dolphins destined for a Cancun water park, saying the sale may be illegal.

But Mexico officials have dismissed the calls saying they have no evidence the animals are being maltreated.

The Solomon Islands haul is thought to be the largest ever, and increases by a fifth the total number of dolphins currently kept in captivity worldwide.

A foreign consortium is believed to be behind the mass capture, promising local fishermen $400 for each dolphin caught.

Rights groups report that many of those captured are being held in small, shallow pens on Gela - an island off the capital Honiara.

The World Society for the Protection of Animals (WSPA) said the animals are transported for hours by boat - facing permanent internal damage by being removed from a weightless water environment.

"This is an animal welfare tragedy and could well have serious impact on the environment," said Ric O'Barry, WSPA's marine mammal specialist.

Interventionist forces

The fate of the dolphins is complicated because of the political state of the Solomon Islands, which has been in chaos since the end of an ethnic war three years ago.

Australia and New Zealand, due to send in intervention forces, are being urged by animal rights groups to ensure the safety of the captured dolphins.

Australia's Environment Minister David Kemp urged Mexico to halt the import saying it may be flouting international law, which prohibits the trade in dolphins if it is detrimental to them and harms the environment.

He added: "We are also communicating our concern to the Solomon Islands, however we believe that on-ground action ... may be difficult in light of that country's current situation".

Mexico responded by saying it "saw no reason to block" a permit given to Cancun's Parque Nizuc in April for the import of the dolphins.

Georgita Ruiz, of Mexico's Environmental Protection Agency, said the animals were expected to arrive in Mexico in "a few days".